The present invention relates to a shutter apparatus for use with lighting sources, particularly stage lighting instruments, whereby the size and shape of a light beam projected by the lighting source may be varied.
Framing shutters have been used in stage lighting instruments, or luminaires, to vary the size and shape of a light beam projected. Typically, four manually adjustable blades having straight edges are inserted through slots in the housing of a spot light luminaire at a position along the optical system of the luminaire, such as at a projection gate, where an image may be formed and projected. These framing shutters are often used to xe2x80x9cframexe2x80x9d a normally circular or ellipsoidal spot of light into a rectangular or other quadrilateral form, such as to simulate the effect of sunlight shining through a rectangular window and casting a quadrilateral patch of light on a floor.
Examples of framing shutters are well known in the art as illustrated, for example, in U.S. Pat. Nos. 1,767,756; 2,076,240; 2,950,382; 3,307,028; 3,571,588; 3,594,566; 4,208,100; 4,210,955; 4,232,359; 4,468,720; 4,890,208; 5,446,637; 5,510,969; 5,904,417; and in other patent publications including GB-A-2270969 and WO-A-96/36834.
Prior implementations of framing shutters have been developed to provide three main features or functions. Shutter blades can be moved orthogonally into a light beam to form a rectangular beam. Shutter blades can be skewed non-orthogonally to form a trapezoidal or other non-orthogonal beam. The set of shutter blades can be rotated as a unit around the longitudinal axis of a light beam to rotate the resulting shape of the beam, as desired. The shutter blade apparatus is made as thin as possible to keep the shutter blades within the depth of field of a spotlight optical system, while making the shutter blades heat resistant so they do not warp.
Shutter blades are made large (wide) so they can be moved non-orthogonally and still intercept the light beam. This requires a large amount of space within the plane of movement of each shutter blade to afford this freedom of movement.
Prior implementations of framing shutters for motorized and remote-controlled lighting instruments, particularly for stage lighting or other entertainment lighting applications, require pivot couplings or other linkages between the shutter blades and the driving mechanisms. These couplings and linkages require additional components, thereby increasing the depth or thickness of each mechanism, which increases both the cost and complexity of the framing shutter apparatus. Installation of the couplings increases the complexity of manufacturing the framing shutter apparatus.
The invention provides a simple and inexpensive light beam shutter control method and apparatus for use in a luminaire or other light projection device. The present invention comprises one or more shutter blades having at least one edge for intercepting at least a portion of a beam of light projected by the light projection device and a pair of curved driven surfaces formed in the periphery of the shutter blade. A pair of linear driving elements is coupled to the shutter blade at the driven surfaces to extend and retract the blade to position the blade edge into and out of the beam of light.
In one aspect of the invention, each of the linear driving elements can be actuated independently and in opposite directions relative to the periphery of the shutter blade to rotate the blade and the blade edge relative to the light beam.
In another aspect of the invention, the light beam shutter apparatus may include a plurality of shutter blade mechanisms in various orientations and assembled as a shutter mechanism assembly, which may be rotated about a central axis through which a beam of light passes.